Method of and apparatus for reacting magnesium with a volatile metal halide



Nov. 25, 1958 D. s. cHlsHoLM E1-AL 2,861,791 METHOD oF AND APPARATUS Foa REACTING MAGNESIUM WITH A VOLATILE METAL HALIDE Qriginal Filed 001;. 20, 1952 3 Sheets-Sheet l ATTORNEYS Nov. 25, 1958 D. s. cHlsHoLM ET AL 2,861,791

4 METHOD OF' lAND APPARATUS FOR REACTING MAGNESIUM WITH A VOLATILE METAL HALIDE Original Filed Oct. 20. 1952 3 Sheets-Sheet 2 I My ,var/ic/es 67 2,0 "n 5B 5 65 IEE. :y2 V

"iff"- 0049/0.: S. CI/nls/m/m By Don Fi Ha// A TTORNE YS NOV- 25, 1958 D. s. cHlsHoLM ET AL 2,861,791

METHOD OF AND APPARATUS FOR REACTING MAGNESIUM WITH A VOLATILE METAL HALIDE Original Filed Oct. 20, 1952 3 Sheets-Sheet 3 1N V EN TORS.

'Y Q. M

A 77j ORNE YS 2,861,791 ivmTHoD or AND APrARArUs FOR` REACT- WG MAGNESIUM'WITH A VOLATILE METAL HALIDE nmiglas s". Chisholm' and non F. Hall, Midland, Mich., assignors to The Dowhemical Company, Midland, Mich., a corporation of Delaware original appiieatin otob'er 20, 1952,5eria11N0. 315,604. Divided and this application September 16, 1957, Serial No. 684,282

The invention relates to a method of and apparatus for thev reduction of a metal halide vapor with magnesium. It more particularly concerns an improved method of and apparatus for the productionV of theA metals, titanium and zirconium, by reacting a-volatile halide thereof, especially the tetrachloride, with magnesium.

Heretofore in the reduction of titanium tetrachloride, for example, in accordance with the r'eactiont 2Mg-|-TiCl4=Ti'-{2MgCl2`, the magnesium used has been in the form of a pool of the molten metal in a retaining vessel with the upper surface of the pool exposed to the vapor of the titanium tetrachloride. In the ensuing re'action, there is formed a sponge-like mass of metallic titanium in situ, together with molten magnesium chloride as a by-product. A number of disadvantages inure to this practice which limits its usefulness. Among these disadvantagesare that some of the magnesium becomes occluded in the titanium sponge and is thus prevented from being used, thereby vlowering the e'iciency of the reduction operation. The sponge so-formedin situ sticks to the walls of and tends to form a bridge in the retaining vessel and is diflicult to remove, in spite of the fact that the magnesium metal during the reduction more or lessl floats upon molten magnesium chloride. vAnother disadvantage is that the reaction tends to get out of control allowing the magnesium to overheatand vaporize, thereby producing an undesirable flame-like reaction in which the magnesium burns as a Vapor in the ytitanium tetrachloride vapor forming dust-like particles of metallic titanium instead of sponge. The dust-like particles of titanium thus produced are exceedingly diiicult, if not nited States Patent impossible, to recover as massive titanium metal.

Another disadvantage is that the titanium sponge is bulky and very reactive while hot necessitating essentially batchwise operation to permit cooling for the' removal of the sponge from the retaining vessel and replacement of the supply of magnesium metalfor the reduction. Similar diiculties arise in the reduction of zirconium tetrachloride with magnesium. Insofar as we are aware, there is neither a method or an apparatus extant for the production of either titanium or zirconium metal by the reduction of the tetrachloride of these metals with magnesium which are not hampered in one way or another by the foregoing diiculties. Accordingly, it is the principal object of the invention to provide an improved method of and apparatus for carrying out the reduction of the aforesaid halides without the diiculties attendant upon the use of the conventional methods yand means. Other subjects and advantages will become apparent as the description of the invention proceeds.

Pursuant to the present invention, it has been discovered in reacting titanium tetrachloride vapor, for example with magnesium, that by particulating the magnesium and laying down a train or'elongated pile ofthe magnesium particles upon a heat controlled supporting surface in an atmosphere of titanium` tetrachloride vapor, ignition and smoldering of the powder'- occurs in zonesv of the train intermediatelits ends which'. move pregrei 2,861,791 Patented Nov. 25, 19 58 sively and relatively slowlflng the train away from the zone'of formation the particles are brought to ignition temperature'. At thesanietime by abstrct'ing suicient of the resulting heat of the' reducing reaction from' the smoldering mass of magnesium particles throgh the supportingsurface, they are prevented from bursting into Haine and the reacting" particles` are maintained a smoldering state until consumed. The particles of magnesi'm thus trete'dch ateinp'rature at least ,abeve that of the molten magnesium chloride formed in' tthe reaction as a' by-prodnet, butthe particles do n ot run together, instead they remain asV a porous mass, thereby providing interstices'i thi'nghout the pile; Thetitanium tetrachloride impor thereby elld t p'rmea the pile andl use all the fnagn'e'si'liin pa`1rt'i ?:les', and` mcli of the molte'- magnesium chloride is" able to moreor less drain away from the smoldering portion of the train' as the reaction proceeds.` As' a result, there is formed in situ atitanium sponge occupying a'- space about twice that of thet consumed' train 'or pile of magnesium particles withoutprodu'cing titaninm metal dust, the sponge being substantially free from unreacted magnesium metal'. Moreover, the sponge so-pr'o'duced' may be readily removed from the supporting surface beyond the smoldering zone of the train' without interrupting the reduction operation; The method is preferably carried out in' continuous mannerby continuously lengthening the train or pile of magnesium particles .atone end ahead of the smolderingV portion, at aV rate sutlicient to keep' a supply off magnesium `particles ahead of the smoldering' ones, while r'eirioving the produced sponge from the other end behind the smoldering portion; Analogo'us' resultsV are obtained on Vapplying the same methodV with zirconium tetrachloride vapor. YThe invention then consists 'of the improved method and apparatusherein'fully described and particularly pointed out in the claims, the annexed drawingfand following description setting ,forth various modes of practic g the invention.

In the said annexed drawing,

Figi lis a schematicv diagram illustrating the method of the invention together with apparatus for practicing the saine; j ,4

' Fig 2" is side elevation largely in section of an apparat'usa'c'cor/dingF to theiny'ention. A

Fig; 1s a horizontal section of the apparatus on the line s-:s 6ft-fig.- 21.-

On referri o Fig. 1,- it will be apparent that this is `a diagraminat representation of the method generally outlined abovel and the gre illustrates the kprinciple of carrying 'out the reaction in accordance with the invention, `as applied f6 die pred fion o f titanium, foi exam-j ple, Vby a controlledA smoldering'of a train ofi* pile`V of particles of magnesium; inl an' atmosphereof titanium tetrachloride vap'r. Iii th'isfgr is shwn a support'- ingA surface 1, on` which tli'e reaction of the magnesium' particles with the halide'vapor is to take place` The"I supporting surface' is' provided with 'teiriperatii re control means comprising-'a set' of pipes" 2, embe ded in the supportingsurface, thoughwhich airat a suitable teni-:1 perature'may be passed The supportin'gsurfaceisplaeed Within ran enyelope,- not shown; for"retaining an ambient` atmosphere 3 of titanium-tetrchlor`ide va'poi with"vthielri y`'sium. particles.are -toreact: MeansV are pro?` isV 'the particle feeder 4,- above'the supporting? siir'iacet r; depositing thereon the magnesium-r particles, the rate' of' epositionf being subject to control, as iby mean ofthe v'alveS. With this apparatus, a train `of particulated magnesium is shown asf havin bee" dc pc'sited,v ipoiiftlieV supporting surf a relativ' si wia outlet 6 with'- resp ct the po ng srfaeehinthe directies@ ofi lfilto'fiigiit THe-*train* er p'rtl'es' 6- mo ement v,ofthe feederI Y 3 Y formed passes through a number of changes occurring in sequence in more or less distinct zones moving along the train in the ensuing reaction which consumes the train as it forms leaving titanium sponge in situ. Y

As to these changes, the train begins, as aforesaid, with the deposition of the particles on the supporting surface. This takes place at the pileor train-forming zone 7 below the feed pipe 6 from which the particles fall. The particles at this stage are relatively cold that is the temperature .is below that at which they will spontaneously ignite in the tetrachloride atmosphere. The pile-forming zone is followed by a preheating zone 8 in which the particles are subjected to heating both by contact with the supporting surface and by contact with adjacent particles already ignited andburning in the following'zone. The heating which occurs in the preheating zone raises the temperature of the particles progressively along the preheating zone to a temperature at which ignition or burning of the magnesium' particles in the halide atmosphere begins. Thus, an ignition zone is established adjacent to the hotter end of the preheating zone, as indicated by numeral 8, the hotter end being remote from the zone of formation. The ignition zone on the forward end is sharply distinct from the preheating zone while the rear of the'ignition zone merges into a smoldering zone designated by numeral 10 where the particles become hotter as the reaction proceeds. In the front of the smoldering zone, the ignited particles communicate some of their heat to adjacent unignited particles and as Aalready mentioned thereby maintain ignition in the ignition zone. Burning of the particles continues in the smoldering zone until all magnesium particles are consumed forming titanium sponge in situ as a loaf or cake and molten magnesium chloride.

In the smoldering zone, more than enough heat is liberated to maintainthe'reaction at a smoldering pace, and accordingly, in this zone, the smoldering particles are subjected to a heat exchange in which a sufficient amount of the heat of the vreactionis abstracted from the pile as though the supporting surface, by means of a cooling air blast through pipes 2, to prevent the smoldering particles from overheating and bursting into ame. The amount ofheat exchange required to maintain the burning of the ignited particles at a smoldering pace is readily ascertained by trialk as bywatching the smolderingizone and suppressing the reaction bycooling the supporting surface enough to prevent flame formation. It has been found that by maintaining the supporting surface under the smoldering zone at a temperature suflicient to cause ignition of the particles in the halide atmosphere but not in excessof about 900 to 950 C., the reaction rate can be maintained at a smoldering pace. A preferable temperature for the supporting surface is above that sufcient to maintain the by-product magnesium chloride in the molten state (e. g. about 708 C.) but less than about 850 C. Temperatures lower than the melting point of magnesium chloride can be used (e. g. 600 C.) if the solid magnesium chloride which then tends to collect upon the supporting surface can be. removed.

Both during and for some time afterithe smoldering action, a substantial proportion of the magnesium chloride drains out of the sponge. The zone of such drainage of the train is indicated at 11 andvpartally overlaps the smoldering zone 10. The resultingk partially drained sponge .12 left at the end of the smoldering zone, after all Ythe magnesium has been consumed in reducing tetrachloride vapor, may be removed from the supporting surface, as by a cooled scraper 13, in the form of chunks of sponge 14.

-The by-product magnesium chloride which in part' 4 for its magnesium content in conventional manner for reuse in the method.

The foregoing method may be conducted advantageously upon a moving hearth or supporting surface which moves sideways away from the train-forming zone beneath the magnesium particle feeder at a rate which 1s equal, on the average, to the rate at which the z one of ignition moves toward the forming end of the tram. In this way, the various zones above described in connection with Fig. l are obtained which remain in the same relative positions and the process is thereby made continuous. In such mode of operation, the path of the train of magnesium particles is preferably made in the form of a segment of a circle as by the use of a revolving supporting surface arranged beneath a magnesium particle feeder which Yremains stationary with respect to the supporting surface on which the feeder deposits the particles as the surface moves.

This mode of operation and an apparatus therefor 1s illustrated in Figs. 2 and 3 which will now be described. In this mode of operation, the supporting surface for the magnesium particles maybe in the form of a hollow air cooled disc 15, for example, secured to the lower end of the hollow drive shaft 16, the disc being within the'reaction vessel 17 which holds the atmosphere containing the titanium tetrachloride vapor to be reduced. The' reaction vessel 17 is supported in a furnace setting 18 by means of which the-disc 15 may be heated to a temperature sufficient atleast to initiate the reaction of the magnesium with the halide vapor to be reduced and preferably to maintain the by-product magnesium chloride in the molten state. The reaction vessel 17 is provided with a gas tight cover 19 for retaining within the vessel the atmosphere containing the halide vapor with which the magnesium is to react. The cover is provided with an opening Z0 through which passes the aforesaid shaft 16. The stuing box 21, secured to the cover around the opening 20, provided a gas tight seal for the shaft 16. rlhe shaft is supported near its upper end by means of the thrust-bearing 22 which resets on support 23. Drive Ypulley 24 is secured to the upper end of the shaft and is driven by means of motor 25 through the reduction gearing 26, pulley 27, and belt 28. Through the hollowV shaft 16 extends the pipe 29 for conveying cooling air to the inside 30 of the disc 15. The lower end of .the pipe 29 carries a pipe T 31 for facilitating the distribution of the cooling air within the hollow disc. The upper end of the pipe extends through the supportingbracket 32 to asource of air, not shown. The return air from the hollow disc, escapes up the annular space 33 between the outside of pipe 29 and the inside of the hollow shaft 16.

The particulated magnesiumv to be deposited upon the disc 15 is introduced into the vessel from a supply hopper 34 through a screw conveyor 35 and feed pipe 36, the outlet 37 of` which is arranged directly over the disc 15 a short j distance inward of its periphery. Receptacle 33 holds a supply of the halide (e. g. liquid titanium tetrachloride) lwhich is vaporized in the vessel 17 and reduced to metal on the disc 15. The receptacle 38 is connected tothe inside of the reaction vesselthrough the cover by pipe 39 having a valve 40 for controlling the rate of introduction Vof the halide into the vessel. A manometer 41 provides a means for ascertaining the difference in the pressure between the atmosphere outside the vessel and that on the inside. Extending through the cover 19 at an oblique angle is a viewing device consisting of a tubc 42 with a transparent-eye-piece 43 through which may be seen the -upper side of the hollow disc 15. The reaction vessel 17 is provided with a hopper bottom 44 on the inside of which is arranged the inclined screw c nveyor45-Y As shown, the screw conveyor comprises the single plate helix 46 wound on the shaftl 47, the helix having small openings 48 therethrough'to allow liquid tondrain so that the conveyor `will not function to elevate v liquid. rIhe lower end of the shaft 47 is journaled in the bearing 49 mounted in the vessel. The upper end of the conveyor extends into an inclined tube 50 which passes through the vessel to the outside. The lower end 51 of the inclined tube extends into the vessel for a sufficient distance to form a seal with the pool 52 of molten magnesium chloride which is maintained in the vessel during operation. The vessel is provided with an outletY 53 belOw the surface 54 of the pool of molten magnesium chloride, thev outlet being provided with a trap S by means of which the level of the surface 54 is maintained above the lower end 51 of theginclined pipe. The trap has an outlet 56 'outside the furnace setting through which molten magnesium chloride is withdrawn from the pool. Thel upper end of the inclined pipe is provided with aV flange 57 to which is secured the cover plate 58. The cover plate is provided with an opening 59 which forms a bearing for the upper end of the screw conveyor shaft 47. Near the upper end of the inclined tube 50 is a downwardly extending T, 60, having a-flanged opening 61 to which may be detachably secured the vessel 6Z`by means of clamps 63.

An air cooled scraper indicated generally by numeral 64 (Fig. 3) is provided over the disc 15 for removingthe metal sponge formed thereon.- As shown, this device comprises a hollow scraper head 65 carried on one end of' a hollow shaft 66 by means of which the head 65 is moved back and forth across the upper surface of the disc asl indicated in dotted outline. The shaft' 66 extends through a tube 67 one end of which is joined to the side of the vessel 17, around an opening 63 therein, and the other extends through the side of the furnace setting 18; A stufng box 69 is provided on the outer end' ofthe tube 67 for making a seal around theV shaft 66; the seal permitting longitudinal reciprocatory movement without leakage of air into the vessel 17. A bearing in theV form of an annular ring 70, together with the stuing'box 69, maintains the Shaft 66 aligned in the bore of tube 67. Reciprocatory motion of the shaft 66 is provided through the link '71 connecting the shaft' with the crank pin 72 on gear Wheel 73 which'is rotated by pinion 74 on motor 75.

Cooling of the scraper heat 65 is eiected by means of the pipe 76 which extends through shaft 66 to near the inside ofthe working face 77 of thefscraperhead. The pipe'761 is connectedby a'ilexible'hose 78`to a source'of air` (not shown). The air delivered by the pipe 76 to the scraper head exhausts through the annular space '79 between the inside of the shaft 66 and the outside of the pipe 76'.

In operation, as with titanium tetrachloride'for example, the reaction vessel is maintained at a temperature suicient to maintain the pool 52 of magnesium chloride i'n the molten state, the molten magnesium chloride ofthe pools forming-a seal' against the escape of tetrachloride vapor from the reaction vessel through the outlet 53 and tube 50. The tetrachloride to be reduced is introduced into the reaction vessel at a rate preferably sufficient to maintain therein.` a slightly greater pressure of the halide vapor than the atmospheric pressure outside the vessel. Iny starting up, the heating of the vessel by the furnace setting 18 in time heats the hollow disc i5 until it is hot enough toinitiate the reducing reaction between particulated magnesium and the tetrachloride vapor. When the disc is thus made sufficiently hot feeding thereon! ofthe train of particulated magnesium' is begun. This is accomplished by revolving the disc l5 slowly byrstarting motor 25 an'doperating. the screw conveyor 35 so as to convey magnesium particles from the supply hopper 34 to the upper surface` of the disc `15. While magnesium .particles are allowed to fall fromthe outlet 37 into Vthe slowlymoving-,disc E55 a train of particles is thereby 6 ofmagnesiumV particles upon a heated supporting surface in the tetrachloride atmosphere, there is establishedin the train avnumber of more or less distinct zones of action which characterize the method. With the appa= ratus of Figs. 2 and 3, a series of zones similar to that of Fig. 1 is formed Vbut in a train having the form of a segment of a circle instead of a straight line since the train is deposited upon a revolving surface from a xed feeding point. Referring to Fig. 3` in particular, these zones are indicated as follows: pile or train-forming Zone, 81; preheating zone, 82; ignition zone, 83; smoldering zone, 84; drainage Zone, 35; sponge removal zone, 86. The depth of the pile or train is controlled by the rate of actuation of the screw conveyor 35 as well as'by the rate of turning of the disc 15. The depth of the train which gives satisfactory burning or smoldering does not appear to be sharplycriticalt; If the train is relatively thin propagation of the smoldering zone into the preheating.A zone is more or less erratic and discontinuity of operation may result. lf thetrain depth is excessive, there is a tendency for some magnesium particles to be left unburned. Proper depths for the train arel readily ascertained by' trial` during operation and are: evidenced by continuity of the burning or reaction of the magnesium in the tetrachloride'vapor withoutrame, and the absence of unconsumed' magnesium particles inV the resulting sponge. Successful operation has' been had, for example, at depths ranging from 1A: inch to as much as 11/2 inches. f

Inany event, the rate of turning of the disc must not exceed the rate at which' the ignition zone 82 progresses along: the Atrain which becomes heated, then ignite's, and

Smolders in zones progressing along the train as` indicated in the drawing. It will be-understood that the lengths of the. zones isnot critical and varies with operating conditions,and suflicient time should be allowed in4 generating the train forthe smoldering to be completed before removing the sponge from the disc. B-y directingtheviewing tube at the point in the train where the ignition zone merges into the preheating zone, the rate ofturning of the disc can be'adjusted readily to that which will maintain the ignition zone'close to the pilef or train-forming zone S1.

As smoldering proceeds, the temperature' of the smoldering portion of the train tends to rise rapidly and the temperature ofthe hollow disc 15 -is to be controlled and laiddown as indicated 21u89; Asfalre'ady explained in ,i

limited by directing a cooling air blast into it through pipe 78 in amount suflicient to maintain the reaction of the pile ofV particles at asmoldering pace as shown by the absence of flame. The' rate atwhichthe zone of ignition proceedsl along the train of preheated particles, when the desiredsmoldering conditions are reached and operation is continuous, isfor example from about 0.1 to 0.5 foot per minute for particles passing through' a No.'20 sieve with-95I percent retention on a No. 200 sieve and laid in-a train containing per lineal footfrom l to 36 grams of magnesium; For example, a disc, 20 inches in diameter on` which0 isy formed a pile of magnesium particles in the form of a segment of a circle about 2 inches wide and about 21/2 inches from the periphery of the disc, may be turnedv at the rate of about OLZYto 0.6 R. P. M. depending upon the rate of'smoldering. The smoldering zone thusmoves along the sequential train on the disc in a direction opposite to that in which the disc rotates, and, by a suitable'regulation of the speed of rotationrof the disc, isrnaintain'ed constantly at about the same position with respectv to the outlet137-during operation. The by-product magnesium chloride in part drains out-of the resulting sponge in the drainage Zone and drips olf thedisc intothe pool S2 while the disc turns.'

The partially drained sponge left after the smoldering has ceased is periodically pushedor scrapedvoif the dis'c inf chunks by the cooled scraper head65, which'is caused to reciprocatebacky and forth across the path of the train by actuatingmotor75; the Ahead;beingcoole'd sufficiently to prevent the sponge from sticking to it by directing air into the head through the hoser78. With this Vscraper device, the sponge is somewhat compacted on being subjected to the pressure of the scraper head as it pushes against the sponge in scraping it olf the disc, as the sponge is at a temperature generally above 708 C., the melting point of magnesium chloride, and somewhat plastic at this stage. The resulting more or less compacted hot chunks or pieces of sponge fall into the pool SZ of molten magnesium chloride and on actuating the screw conveyor 4S are carried out of the pool through a seal of magnesium chloride in tube 50 into the vessel 62 out of contact with air. After sufficiently cooling the chunks in the vessel, it may be removed from the conveyor and emptied. Much of the by-product magnesium chloride overows through the trap 55 and is discharged at 56, the balance of the magnesium chloride is contained in the pores of the sponge.

The titanium sponge thus produced is readily worked into massive metal by conventional methods to yield a high quality metal.

In providing the particulated magnesium for use in the method, it is desirable to eliminate particles which are dust-like from the feed, although a small amount, such as up to 5 percent by weight, of dust-like particles can be tolerated. In general, it is desirable to use particles larger than those passing through a No. 200 sieve (of the standard screen scale) to avoid loss by dusting. A relatively short drop, `such as 6 inches, from the outlet 37 of the feed pipe to the supporting surface is desirable as the short drop tends to lessen dusting and also undesirable bouncing and rolling of the particles on reaching the supporting surface. Large particlesV are objectionable be cause on melting they coalesce into still larger molten masses which tend to ow off the reaction Vsupporting surface without forming the sequence of zones described. Particles between these extremes may be used and may be produced in various known Ways, such as by grinding, chipping, milling, and atomizing. Particles which are more or less equiaxed, such as those made by the usual atomizing methods, produce the best results. Equiaxed particles as large as those passing through a No. l0 sieve may be used, although somewhat ner particles are preferable, such as those passing through a No. sieve withat least 95 percent retention on a No. 200 sieve.

The particles of magnesium as introduced into the tetrachloride atmosphere, on being caught upon the supporting surface for reaction, are relatively cold so that reaction does not commence to a significant extent until the particles` are actually in the form of a pile or train upon the supporting surface. This Vmode of operation overcomes the clogging at the outlet 37 which can occur when the particles fed through it are too hot or too ne and tend to burn as they fall through the pipey 36. If desired, an inert gas, such as argon or helium, may be fed into the pipe 36 ,as thoughY a pipe connection 64 to block the tendency for the vapor of the volatile halide to enter the pipe 36 from the reaction vessel 17. The dilution, if any, which may result from the presenceeof the inert gas in the atmosphere in the reaction vessel does not significantly affect the reduction reaction, although provision for venting therinert gas from the reaction vessel may be required as by means of a vented condenser, not shown. The particles of magnesium may be deposited upon the hearth or supporting surface at as rapid a rate as that at which the zone of ignition advances in the resulting train or elongated pile. At the same time, the halide to be reduced is introduced into the reaction vessel Lat a rate suflicient to maintain'therein a pressure ofthe halide vapor preferably in excess of the atmosphere pressure outside the vessel. For example, the vapor pressure in the reaction vesel of the halide to be reduced may exceed the atmospheric pressureby l to 20 inches of Water (as in manometer 41) but other pressures may be used.

While the invention has been exemplified with particu; lar reference to the deposition of the train or pile of particulated magnesium upon at surfaces, it is to be understood that other solid supporting surfaces maybe used in similar manner, although 'not flat, such as cylindrical Or conical surfaces. In 'such instances, the cylinder or cone, for example, is arranged to revolve on its axis in such a manner that the underside of a more or less horizontal plane surface Will be tangent to the revolving surface at least at the place where the particles are deposited. It will be found also that even though the supporting surface is madey to slope away from the point of deposition of the particles so as to facilitate drainage of the by-product magnesium chloride, the tendency for the particles to roll off' is reduced, if not completely counteracted, during their reaction with the halide vapor, the reaction products of which give adhesion to the particles for each other and the supporting surface when wet with molten magnesium chloride.

Among the advantages of the invention are that the magnesium, in particular form and arranged in a pile and made to smolder, becomes completely consumed in the atmosphere of the halide to be reduced. There is, therefore, a maximum efficiency of use of the magnesium. The metal obtained from the reduced halide vapor is substantially all in the form of easily recoverable sponge, there being -substantially no produced metal in the form of dust-like particles which are difficult, if not impossible, to recover. The method is adapted to continuous operation without contamination of the metal product by the atmosphere. The reduction operation is subject to easy accurate control by regulation of the input of particulated magnesium metal andlremoval of reaction heat. The magnesium is not fed onto an already reacting body of magnesium instead the magnesium reacts with the halide vapor without hindrance from the magnesium supply for the reaction because the pile or train of magnesium particles used inthe reduction is formed in the reaction zone beforev the reaction occurs. The reaction is confined to the surface of the particles of magnesium in the pile or train; lhence the walls of the reaction vessel enclosing the halide vapor to be reduced do not become fouled up with metal reduced from the halide. The reaction of the magnesium with the halide vapor can be carried out upon horizontal or sloping surfaces without confining sidewalls because the magnesium is in particulate form and the particles neither run together nor olf the surfaces.

This application is a division of copending application Ser. No. 315,604, filed Oct. 20, 1952.

We claim:

1. An apparatus in which to produce in the form of metal sponge a metal selected from the group consisting of titanium and zirconium by the reduction of a volatile halide thereof with the formation of magnesium chloride as a by-product which comprises a reaction vessel adapted to contain the vapor of the halide to be reduced to sponge metal; a furnace setting for the vessel adapted to maintain it at working temperature; a hearth within the vessel and spaced apart from the bottom thereof; a feed pipe associated with the Vessel adapted to convey onto the hearth the magnesium in particulate form; motor means associated with the hearth adapted to move the hearth sideways below the feed pipe whereby the magnesium particles falling from the feed pipe'form a train on the hearth; cooling means associated with the hearth adapted to abstract reaction heat from particles of magnesium reacting on the hearth; and scraper means adjusted to the surface of the hearth adapted to scrape olf the metal sponge formed in situ as the particles of magnesium are consumed on the hearth by the volatile halide.

2. An apparatus in which to produce in the form of metal sponge a metal selected from the group consisting of titanium and zirconium by the reduction of a volatile halide thereof with thejformation of molten magnesiumV sel adapted to contain the vapor of the halide to be reduced to sponge metal; a furnace setting for the vessel adapted to maintain it at Working temperature; a hearth within the vessel and spaced apart from the bottom thereof; a feed pipe associated with the vessel adapted to convey onto the hearth the magnesium in particulate form; motor means associated with the hearth adapted to rotate the hearth below the feed pipe whereby the magnesium particles falling from the feed pipe onto the hearth form a train thereon; cooling means associated with the hearth adapted to abstract reaction heat from particles of magnesium reacting on the hearth; scraper means adjacent to the surface of the hearth adapted to scrape off the metal sponge formed in situ as the particles of magnesium are consumed on the hearth by the volatile halide; cooling means for the scraper; and conveying means adapted to remove from the reacti-on vessel the metal sponge scraped off the hearth.

3. An apparatus in which to produce in the form of metal sponge a metal selected from the group consisting of titanium and zirconium by the reduction of a volatile halide thereof with the formation of molten magnesium chloride as a by-product Which comprises a reaction vessel adapted to contain the vapor of the halide to be reduced to sponge metal; a furnace setting for the vessel adapted to maintain it at Working temperature above the melting point of magnesium chloride; a hearth Within the vessel; a feed pipe associated with the vessel adapted to convey onto the hearth the magnesium in particulate form; motor means associated with the hearth adapted to move the hearth sideways below the feed pipe Whereby the magnesium particles falling from the feed pipe form a train on the hearth; cooling means associated with the hearth adapted to abstract reaction heat from particles of magnesium reacting on the hearth; scraper means adjacent to the surface of the hearth adapted to scrape off the metal sponge formed in situ as the particles of magnesium are consumed on the hearth by the volatile halide; conveying means adapted to remove from the reaction vessel the metal sponge scraped off the 10 hearth; and a shroud around the portion of the conveying means adapted to form a seal with molten magnesium chloride against the escape of halide atmosphere from the reaction vessel.

4. An apparatus in which to produce in the form of metal sponge a metal selected from the group consisting of titanium and zirconium by the reduction of a volatile halide thereof with the formation of molten magnesium chloride as a by-product which comprises a reaction vessel adapted to contain the Vapor of the halide to be reduced to sponge metal; a furnace setting for the vessel adapted to maintain it at Working temperature above the melting point of magnesium chloride; a hearth within the vessel; a feed pipe associated with the vessel adapted to convey onto the hearth the magnesium in particulate form; a metering means associated with the feed pipe adapted to control the rate of introduction of particulated magnesium into the feed pipe; motor means associated with the hearth adapted to rotate the hearth below the feed pipe whereby the magnesium particles falling from the feed pipe form a train on the hearth; cooling means associated with the hearth adapted to abstract reaction heat from particles of magnesium reacting on the hearth; scraper means adjacent to the surface of the hearth adapted to scrape off the metal sponge formed in situ as the particles of magnesium are consumed on the hearth by the voltaile halide; conveying means adapted to renove from the reaction vessel the metal sponge scraped olf the hearth; and a shroud around a portion of the conveying means adapted to form a seal with molten magnesium chloride against the escape of halide atmosphere from the reaction Vessel.

References Cited in the le of this patent UNITED STATES PATENTS 75,294 Ott Mar. 10, 1868 2,556,763 MaddeX .Tune 12, 1951 2,564,337 Maddex Aug. 14, 1951 

1. AN APPARATUS IN WHICH TO PRODUCE IN THE FORM OF METAL SPONGE A METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM AND ZIRCONIUM BY THE REDUCTION OF A VOLATILE HALIDE THEREOF WITH THE FORMATION OF MAGNESIUM CHLORIDE AS A BY-PRODUCT WHICH COMPRISES A REACTION VESSEL ADAPTED TO CONTAIN THE VAPOR OF THE HALIDE TO BE REDUCED TO SPONGE 